Technologies such as microelectronics, micromechanics and biotechnology have created a high demand for structuring and probing specimens within the nanometer scale. Micrometer and nanometer scale process control, inspection or structuring, is often done with charged particle beams. Probing or structuring is often performed with charged particle beams which are generated and focused in charged particle beam devices. Examples of charged particle beam devices are electron microscopes, electron beam pattern generators, ion microscopes as well as ion beam pattern generators. Charged particle beams, in particular ion beams, offer superior spatial resolution compared to photon beams, due to their short wave lengths at comparable particle energy.
Modern semiconductor technology is highly dependent on an accurate control of the various processes used during the production of integrated circuits. Accordingly, the wafers have to be inspected repeatedly in order to localize problems as early as possible. Furthermore, a mask or reticle should also be inspected before its actual use during wafer processing in order to make sure that the mask accurately defines the desired pattern. This is done because any defects in the mask pattern will be transferred to the substrate (e.g., wafer) during its use in microlithography. However, the inspection of wafers or masks for defects requires the examination of the whole wafer or mask area. Especially, the inspection of wafers during their fabrication requires the examination of the whole wafer area in such a short time that production throughput is not limited by the inspection process.
Single beam scanning electron microscopes (SEM) or scanning ion microscopes have been used to inspect wafers to detect pattern defects. However, using a single beam at high resolution can result in a throughput limitation. In order to improve charged particle microscopic techniques several approaches have been suggested. One approach is based on the miniaturization and/or multiplication of the columns, so that several, typically miniaturized columns (in the order of ten to one hundred) are arranged in an array. Each column examines a small portion of the complete sample surface. Thereby, single beam columns can be used, which are simple and robust with respect to their optical characteristics. Another approach is the use of multi-beam optics, which are highly sophisticated. Thereby, the introduction of aberrations due to having multiple beams in one column, typically on different axes, is a serious issue to be considered.
Accordingly, there is a strong desire to provide a charged particle beam apparatus with an increased throughput, wherein the introduced aberrations are reduced.